From: Akashdeep Kaur <a-kaur@ti.com>
To: <praneeth@ti.com>, <nm@ti.com>, <vigneshr@ti.com>,
<alexandre.belloni@bootlin.com>, <linux-rtc@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <sebin.francis@ti.com>
Cc: <s-tripathi1@ti.com>, <vishalm@ti.com>, <k-willis@ti.com>,
<a-kaur@ti.com>
Subject: [PATCH 0/2] rtc: Prevent hctosys from using invalid RTC time
Date: Wed, 21 Oct 2026 09:54:33 +0530 [thread overview]
Message-ID: <20261021042435.3895543-1-a-kaur@ti.com> (raw)
The kernel's boot-time RTC synchronization blindly trusts the RTC
value when setting system time, but RTCs may have invalid time
depending on the boot path:
- On first cold boot: RTC may have lost power, time is invalid
- After low-power mode (RTC-only) cold boot: RTC retained power, time
is valid
On normal cold boot where bootloader or NTP has already established
correct time, boot-time sync (triggered when RTC driver loads as
module or probes at boot) can overwrite it with invalid RTC data,
causing time rollback to 1970. However, on boot from RTC-only power
mode, the RTC has valid time and boot-time sync should work to
restore system time from RTC.
This series adds a flag that drivers set dynamically per-boot to
indicate whether RTC has valid time. Drivers check at probe if RTC
retained power through this specific boot. Boot-time sync checks this
flag before setting system time. This enables correct behavior for
both boot paths while keeping PM suspend/resume compensation
unaffected.
---
Akashdeep Kaur (2):
rtc: Add flag for dynamic hctosys control
rtc: ti-k3: Mark RTC time as invalid without battery backup
drivers/rtc/class.c | 15 +++++++++++++++
drivers/rtc/rtc-ti-k3.c | 7 +++++++
include/linux/rtc.h | 7 +++++++
3 files changed, 29 insertions(+)
base-commit: 8f7df005a7564bd7ffa75da9c3085d5b996f1e16
--
2.34.1
next reply other threads:[~2026-10-21 4:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-21 4:24 Akashdeep Kaur [this message]
2026-10-21 4:24 ` [PATCH 1/2] rtc: Add flag for dynamic hctosys control Akashdeep Kaur
2026-10-21 4:24 ` [PATCH 2/2] rtc: ti-k3: Mark RTC time as invalid without battery backup Akashdeep Kaur
2026-10-21 7:13 ` [PATCH 0/2] rtc: Prevent hctosys from using invalid RTC time Alexandre Belloni
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